The present invention is generally related to the handling of continuous, thin and delicate webs of any material.
More particularly, the invention is directed to a feeding device for such webs towards a work station, particularly but not exclusively to a forming press, of the type comprising longitudinal support and guiding means of the web and step-feed means of the web onto said support and guide means along a longitudinal direction, wherein the feed means comprise a stationary gripper and a movable gripper each including a fixed jaw and a movable jaw placed transverse to and on opposite sides of the web, a pneumatic actuator assembly for operating linear alternative forward and back displacement of the movable gripper relative to the stationary gripper parallelly to said longitudinal direction and opening and closure of the movable jaws of said grippers relative to the respective fixed jaws in synchronism with the alternative displacement of the movable gripper, and an adjustable stop member cooperating with the movable gripper at the end of the forward displacement thereof.
Feeding devices of the above-mentioned type are currently manufactured and marketed by ELMER of Turin, Italy. Traditionally, in these known feeding devices the longitudinal support and guide means of the web between the jaws of the two grippers comprise a pair of superimposed endless upper and, respectively, lower belts, maintained in a stressed condition by respective pairs of rollers and having, respectively, a lower run and an upper run facing each other and between which the web material is longitudinally supported and guided. The web and the adjacent runs of the two endless belts are interposed between the fixed jaws and the movable jaws of the two grippers, and the disposition is such that the fixed jaws, along with the pneumatic actuator assembly and said adjustable stop member, are contained within the loop of the lower belt, while the movable jaws of the grippers are placed within the loop of the upper belt.
Evidently, the combined opening and closure movements of the movable jaws of the two grippers and the alternative synchronised displacement of the movable gripper produce translation of the two endless belts and the consequent step advancement of the web material inserted therebetween, along the longitudinal feed direction.
In order to modify the feed-step setting of the web it is sufficient to change the position of the adjustable stop member, increasing or decreasing the distance thereof relative to the stationary gripper.
However, owing to the above disposition, in the feeding devices presently known the step setting operation generally involves problems generated by difficult accessibility of the stop member.